A. Do you want each Manager to book and attend each Monday session throughout 2013?
B. Do you want them to book individual sessions because you can not accomodate everyone each Monday?
If A, then create one activity with one session containing multiple dates (every Monday) and have them book that event.;
If B and its first come first serve, then you would have to create an activity for each Monday session throughout the year. Again, you will find some discussion on signing up for multiple sessions in the same activity, but I'm not sure that anyone has enabled this in a recent release with custom code. It's definitely not doable with the current release.